Age, sex and weight matched groups of genetically normal, prediabetic and diabetic Pima Indians and normal Caucasians were examined by means of oral and intravenous glucose tolerance tests, arginine infusions, in vivo insulin resistance measurements, glucose clamp technique and circulatory mononuclear cell insulin receptor assays, and urinary protein profiles to determine whether abnormalities of insulin, glucagon secretion or other measurements are characteristic of the prediabetic, diabetic, obese and nonobese states.